Very Strange!!!!

[Alfie Moon]

I own a mk 2 1990 golf gti digi.  When the car is sat still the water circulates fine the oil temp is good around 94 - 96, water temp is 1/4 of the way up the gauge, the radiator fan kicks in as it should.  The problem is when you give the car a little thrash the radiator seems to stop working, water then starts to come out through the expansion tank, water temp and oil temp both shoot up and I have to pull over as usual and stop.  Have replaced most things, head has been rebuilt and pressure tested, new radiator, expansion tank, samco hoses, water pump, blue expansion tank cap, oil cooler, oil filter, heater matrix.  Really running out of ideas now and i am starting to fall out of love with my VW so please any ideas would be very appreciated.

Does not loose any water when doing a constant 60 - 70.

[fused]

did you replace the thermostat? might want to try a lower temp thermostat, awesome gti do one from neuspeed. almost sounds like a pipe or rad is blocked/resticted. I would try flushing the system with pressure if possible?? back flush the rad incase it has become blocked..... did you by the expansion and cap from VW or elsewhere? I tried some other places but they failed, had to go back to VW for these parts!

Good luck

[Alfie Moon]

yes i replaced the thermo as well.  Both the thermo and expansion tank cap were from  GSF. Have flushed the system out as well.

[rubjonny]

check the thin hose to the top of the header tank isnt blocked, when you rev the engine you should see a stream of water coming out oif the hole in the top of the tank.  Failing that perhaps your tank has a crack in it, or its a poor quality one.